On Mon, Dec 6, 2021 at 11:59 AM Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
On 06/12/2021 07:00, Muni Sekhar wrote:
On Sat, Dec 4, 2021 at 3:18 AM Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
Hi Sekhar,
On 03/12/2021 17:50, Muni Sekhar wrote:
Hi All,
We have a Digital PLL with 64 bit timer counter hardware and the counter is accessible from the CPU over the PCIe bus.
Is it possible to add this timer counter hardware as new clocksource driver? To do this, can someone please point me to the existing reference source code(or patch) for this task.
You can refer to the drivers located in drivers/clocksource
I don't see the option in menuconfig to build the clocksource driver as a loadable kernel module, for example CONFIG_X86_PM_TIMER=m instead of CONFIG_X86_PM_TIMER=y. So a clocksource driver should always be part of the kernel built-in module?
Yes, that is the case today.
If so, what's the reason for that?
The timer is a component needed at boot time, so a module version does really not make sense.
So I would return back the question : what is the reason for a module?
For built-in module we need to compile the whole kernel, but we are currently using the kernel via linux-image-4.15.0-54-generic.deb file installation.
git annotate on one of the driver can give you the initial commit where recent submissions explain the timer internals.
Suppose if it is possible to add a new clocksource driver for this hardware then does any userspace get_timestamp* API would get the time from this new hardware?
It should if the timer is selected as the clocksource
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-- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
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-- Thanks, Sekhar